Icing Tests Research Articles

Wind tunnel tests of the rime icing characteristics of a straight-bladed vertical axis wind turbine

For the wind turbines installed in the cold and humid regions, icing accretion on the blade surface seriously degrades its performance. The Straight-Bladed Vertical Axis Wind Turbine (SB-VAWT) is also troubled by the problem. For exploring the characteristics of icing, the icing wind tunnel tests have been carried out in this paper. An icing wind tunnel experimental system is designed and fabricated. The experimental parameters in the icing wind tunnel system are measured. A rotor test stand with two blades of NACA0018 airfoil is designed and amounted in the icing wind tunnel. The icing test is conducted under the different tip speed ratios and the rime ice condition. The experimental results show that the rotational speed of the blade has significant effects on the characteristics of icing. When the tip speed ratio is lower than 1, the ice layer covers in the whole blade surface and grows layer by layer. As the tip speed ratio is higher than 1, the ice layer mainly concentrates in the vicinity of the leading edge. Three factors, which are the relative angle of attack, the rotational position of blade and the centrifugal force, influencing on the characteristics of icing are analyzed and discussed.

Diagnostic yields and clinical features of ocular myasthenia gravis.

To investigate clinical features and diagnosis process of ocular myasthenia gravis (OMG) in ophthalmology department.A total of 36 patients with ptosis or diplopia who had follow-up for at least 3 months between March 2016 and December 2019 were included in this study. Clinical symptoms of patients and the test results were analyzed. According to the positivity of serologic test, these patients were divided into 2 groups (confirmed OMG and possible OMG with relief of symptoms after antimyasthenic treatment) for comparison.Ptosis was present in 12 (33.33%) patients, diplopia was present in 14 (38.89%) patients, and both ptosis and diplopia were present in 10 (27.78%) patients. Acetylcholine receptor auto-antibody (AchR Ab) was positive in 14 (38.89%) of 36 patients and ice test was positive in 15 (71.43%) of 21 patients with ptosis. Unequivocal response to pyridostigmine was observed in 31 (86.11%) patients. For seropositive cases, AchR Ab titer was significantly higher in the group with 2 clinical symptoms than that in the 1 clinical symptom (P = .011).This study presents the usefulness and diagnostic validity of antimyasthenic treatment for OMG, especially seronegative OMG, with detailed symptom analysis.

빙마찰계수에 따른 쇄빙탱커의 빙저항 변화

This study describes the model tests in ice according to the frictional coefficient of an ice-breaking ship and the change in ice resistance by the analysis method for each component of ice resistances. The target vessel is a 90K DWT ice-breaking tanker capable of operating in ARC7 ice conditions in the Arctic Ocean, and twin POD propellers are fitted. The hull was specially painted with four different frictional coefficients on the same ship model. The total ice resistance can be separated by ice breaking, ice buoyancy, ice clearing resistances through the tests in level ice, pre-sawn ice and creep test in pre-sawn ice under sea ice thickness of 1.2 m and 1.7 m. Ice resistance was analyzed by correcting the thickness and bending strength of model ice by the ITTC correction method. As the frictional coefficient between the hull and ice increases, ice buoyancy and clearing resistances increase significantly. When the surface of the hull is rough, it is considered that the broken ice pieces do not slip easily to the side, resulting in an increase in ice buoyancy resistance. Also, the frictional coefficient was found to have a great influence on the ice clearing resistance as the ice thickness became thicker.

Boundary Conditions for Compressor Cascade Ice Crystal Icing Testing

Abstract At the Altitude Test Facility (ATF) of the University of Stuttgart, a linear compressor cascade test rig serves the investigation of ice crystal icing (ICI) under engine realistic conditions. A numerical model of the first stage of National Aeronautics and Space Administration (NASA) Stage 67 is validated with experimental data taken from the literature and used to investigate the respective ice crystal icing conditions for prospective cascade experiments. Eleven operating points simulating climb conditions with constant non-dimensional power setting through ascending parcels of moist air are selected for analysis. Only the melting-dominated regime is considered. The three-dimensional flow field is obtained using a Reynolds-averaged Navier–Stokes (RANS) approach in combination with a Spalart–Allmaras one-equation turbulence model. The droplet and ice crystal trajectories are calculated based on an Eulerian framework. The computation of the surface energy balance is adapted from the Messinger model taking into account unsteady phenomena. Four of 11 selected operating points indicate the onset of substantial ice accretion. A static wet-bulb temperature of freezing constitutes in general the lower icing limit for rig experiments. The upper icing limit depends on the ice water content impinging and sticking to the target surface.

Research and Development of a Small-Scale Icing Wind Tunnel Test System for Blade Airfoil Icing Characteristics

In order to study the icing mechanism and anti-icing technology, a small low-speed reflux icing wind tunnel test system was designed and constructed. The refrigeration system and spray system were added to the small reflux low-speed wind tunnel to achieve icing meteorological conditions. In order to verify the feasibility of the test system, the flow field uniformity, temperature stability, and liquid water content distribution of the test section were tested and calibrated. On this basis, the icing tests of an aluminium cylinder, an NACA0018 airfoil, and an S809 airfoil were carried out, and the two-dimensional ice shape obtained by the test was compared with the two-dimensional ice shape obtained by the numerical simulation software. The results show that in the icing conditions and icing time studied, the parameters of the test system are stable, and the experimental ice shape is consistent with the simulated ice shape, which can meet the needs of icing research.

The research on floe ice force acting on the “Xue Long” icebreaker based on synthetic ice test and virtual mass numerical method

The research on floe ice force acting on the “Xue Long” icebreaker based on synthetic ice test and virtual mass numerical method

Comparative evaluation of HET-CAM and ICE methods for objective assessment of ocular irritation caused by selected pesticide products

Eye irritation potency of pesticides (fungicides, herbicides, insecticides) was comparatively tested by HET-CAM and ICE method. Based on the results of the tests the statistical analysis of agreement between classification using individual methods was done by Goodman-Kruskal's rank correlation and determination (calculation) of Cohen's kappa coefficient. Statistical analysis of agreement between classification revealed significant correlation between results of in vivo and in HET-CAM assays (76%). There was no significant correlation between result of in vivo and in ICE methods (64%). Weakest correlation was found between the data from in vitro HET-CAM and ICE tests. The percentage of agreement between two in vitro data was 48%. They may be recommended as a part of a battery of tests to reduce experimentation on mammals and to limit or eliminate pain and injury inflicted on experimental animals. The HET-CAM test is a useful tool for studying in vivo the potential conjunctival irritation, while the ICE test can be used to study corneal irritant effects in detail.

Experimental investigations on the level ice resistance of ships with non-typical icebreaking bow shapes

ABSTRACT For non-typical icebreaking ships with high stem and/or small waterline angles, the hull–ice interaction process in level ice comprises a combination of many different phenomena which is difficult to be described by existing straightforward approaches. In order to gain knowledge about the level ice resistance of ships with non-typical icebreaking bow shapes, a methodology to improve the principal understanding of the hull–ice interaction process, ice failure, level ice resistance and its distribution along the ship hull during model scale ice tests is developed. For this purpose, one ship model has been manufactured and extensively instrumented. By performing resistance tests at several loading conditions, in model ice sheets of different thickness and at multiple speed values, relevant information on the nature of ice resistance of such ship type can be obtained. In this paper, the methodology is briefly summarized and part of the results of the model testing campaign are presented and discussed.

Comparison of different droplet measurement techniques in the Braunschweig Icing Wind Tunnel

Abstract. The generation, transport and characterization of supercooled droplets in multiphase wind tunnel test facilities is of great importance for conducting icing experiments and to better understand cloud microphysical processes such as coalescence, ice nucleation, accretion and riming. To this end, a spray system has been developed, tested and calibrated in the Braunschweig Icing Wind Tunnel. Liquid droplets in the size range of 1 to 150 µm produced by pneumatic atomizers were accelerated to velocities between 10 and 40 m s−1 and supercooled to temperatures between 0 and −20 ∘C. Thereby, liquid water contents between 0.07 and 2.5 g m−3 were obtained in the test section. The wind tunnel conditions were stable and reproducible within 3 % standard variation for median volumetric diameter (MVD) and 7 % standard deviation for liquid water content (LWC). Different instruments were integrated in the icing wind tunnel measuring the particle size distribution (PSD), MVD and LWC. Phase Doppler interferometry (PDI), laser spectroscopy with a fast cloud droplet probe (FCDP) and shadowgraphy were systematically compared for present wind tunnel conditions. MVDs measured with the three instruments agreed within 15 % in the range between 8 and 35 µm and showed high coefficients of determination (R2) of 0.985 for FCDP and 0.799 for shadowgraphy with respect to PDI data. Between 35 and 56 µm MVD, the shadowgraphy data exhibit a low bias with respect to PDI. The instruments' trends and biases for selected droplet conditions are discussed. LWCs determined from mass flow calculations in the range of 0.07–1.5 g m−3 are compared to measurements of the bulk phase rotating cylinder technique (RCT) and the above-mentioned single-particle instruments. For RCT, agreement with the mass flow calculations of approximately 20 % in LWC was achieved. For PDI 84 % of measurement points with LWC<0.5 g m−3 agree with mass flow calculations within a range of ±0.1 g m−3. Using the different techniques, a comprehensive wind tunnel calibration for supercooled droplets was achieved, which is a prerequisite for providing well-characterized liquid cloud conditions for icing tests for aerospace, wind turbines and power networks.

Maximal Oxygen Consumption Requirements in Professional North American Ice Hockey.

Ferland, P-M, Marcotte-L'Heureux, V, Roy, P, Carey, V, Charron, J, Lagrange, S, Leone, M, and Comtois, AS. Maximal oxygen consumption requirements in professional North American ice hockey. J Strength Cond Res 35(4): 1586-1592, 2021-This study was designed to measure preseason on-ice relative V̇o2max of professional ice-hockey players (n = 101 National Hockey League [NHL], 42 American Hockey League [AHL], 4 East Coast Hockey League [ECHL], and 15 Canadian Hockey League [CHL]) throughout 17 years and compare it between generations, league level, and position, and to verify if it was related to season and NHL career statistics. Relative V̇o2max was measured on ice with a portable metabolic analyzer (K4b2, Cosmed, Rome) with full hockey equipment, except for the helmet with either the Skating Multistage Aerobic Test or the 30-15 intermittent ice test tests. Relative V̇o2max results from both tests were compared between players of the same generation with an independent-samples T-test and were not significantly different. A one-way analysis of variance and post hoc pairwise tests were performed to detect significant differences between groups. Pearson correlations (two-tailed) were also performed between selected variables. All statistical significance was set at p < 0.05. Results show that there are no significant differences for relative V̇o2max between generations (2001-2003 vs. 2006 vs. 2015-2017), league level (NHL vs. AHL vs. ECHL vs. CHL), and position (winger, center, and defense), other than the ECHL being lower. There are also no significant relationships between V̇o2max values and hockey season and NHL career statistics. Thus, the results show that there is a minimal relative V̇o2max requirement to play North American ice hockey at the elite level (55.9 ± 5.2 ml·kg-1·min-1; n = 162). Future research should be directed toward comparing V̇o2max of elite and amateur ice-hockey players to confirm the minimal relative V̇o2max requirement to play North American ice hockey at the elite level.

Novel dc flashover model for predicting flashover voltage of the iced insulators

This work first proposes a novel flashover model based on the deduced residual resistance of the ice layer. The most important finding of the field icing tests is that the double-layer ice-melting water film exists on the inner and outer surfaces of the ice layer. The conductivity of melting water on the inner and outer surface of the ice layer has been measured, and the corresponding surface conductivity has been calculated. According to the proposed flashover model, the ratio η of the resistance of the ice layer to that of the pollution layer gradually increases with the increase of the ratio k of the resistance of the outer surfaces to that of inner surfaces, and eventually approaches saturation. Furthermore, the icing flashover criterion has been modified, and the voltage gradient of the inner surface is less than that of the outer surface. Test results show that the ice flashover voltage is lower than the pollution flashover voltage between 2.18–9.69% and 14.75–20.32% under light ice and semi-cylindrical ice, respectively. The simulation results based on the proposed model and the classic model are compared with the field test data. Results show that the proposed model could attain a high accuracy of dc flashover voltage and demonstrate the effectiveness of the proposed model.

Fabrication of superhydrophobic, self-cleaning and anti-icing ZnO/PTFE-SiO2 nano-composite thin film

In the present study, we have been using a two-step process to create a super-hydrophobic property on the copper surface. We first created micro and nano-scale roughness by applying ZnO layers on the copper surface, then immersion the samples in a PTFE-SiO2 suspension at specific times to reduce the surface energy. We also investigated the effect of silica nanoparticle concentrations, ZnO layer numbers and sample immersion time in the PTFE-SiO2 suspension on the surface hydrophobicity. The morphology and chemical analysis of the coating surface were studied with Field Emission Scanning Electron Microscopy (FESEM) and Infrared Fourier Transform Spectroscopy (FTIR) methods. The water contact angles on the prepared samples were measured by a water contact angle analyzer method. Icing tests were performed at a constant operating temperature of −8 °C. Also, the self-cleaning behavior of the samples was evaluated by an iron oxide powder. The results indicated that the ZnO/PTFE-SiO2 coated copper substrate showed superhydrophobic (CA, 164°), anti-icing (icing time 700 s) and self-cleaning properties.

Fabrication of transparent silica-silica nanotube/PFTS nano-composite thin films with superhydrophobic, oleophobic, self-cleaning and anti-icing properties

Light on optoelectronic devices and solar panels is lost both through reflection at the air/glass interface of the cover glass and through scattering or absorption by accumulated dust, dirt and ice. Therefore, the transparent superhydrophobic thin films can resolve these problems. In this research, silica-silica nanotube nanocomposite thin films were applied on glass substrates by a sol–gel method. To modify the nanocomposite thin film, the samples were immersed in a PFTS solution. The morphology, chemical composition and transparency of the thin films were investigated using FE-SEM, FTIR and UV–VIS–NIR spectrophotometer methods. The water and oil contact angles on the thin film surfaces was measured using a contact angle analyzer. The self-cleaning and stability of the thin films were investigated. The water contact angle results indicated that silica nanotube/PFTS thin films increased water contact angle of the glass substrate from 16° to 152°. The transmittance of the silica-silica nanotube/PFTS coated glass substrate was measured as 87% at 550 nm. The icing test results showed that superhydrophobic coating increased icing time during ice formation on the glass surface from 102 to 874 s.

Balance assessment after altering stimulation of the neurosensory system.

Aim Posture requires fine integrative elaboration, performed by the central nervous system, of neurosensory information originated from the visual, vestibular and spinal circuit. Many perturbing agents can influence this elaboration and then the postural stability. Several studies have evaluated only the effect of a single agent on the postural control. The study analysed the perturbing effect of several external agents on the different sensorial circuits in terms of postural balance loss in orthostatism. Methods The postural stability of 31 patients was evaluated with a static posturography platform in basal conditions and after exposure to an external agent in the following order: stroboscopic light projecting, mechanical rotations on a swivel chair, feet desensitization through ice, administration of an alcoholic drink at intervals which depended on the participant return to basic posturographic values. Tests were performed with open eyes (OE), closed eyes (CE) and reducing plantar perception through the use of a rubber pillow. Results The stroboscopic light altered the postural control. The swivel chair disturbed only with CE. Ice and alcohol increased the oscillation area. The alcohol test had a significant reduction in postural control with OE compared to CE. The rubber cushion increased the oscillation area in all OE tests and with CE in alcohol and ice tests. Conclusion The different agents did not trigger postural control deficits in the same way. A cold environment with psychedelic lights and the use of alcoholic beverages altered significantly the postural stability by influencing simultaneously all perceptions (visual, vestibular and somatosensory feedback).

An Experimental Study on Segmented-Encapsulated Electrode Dielectric-Barrier-Discharge Plasma Actuator for Mapping Ice Formation on a Surface: A Conceptual Analysis

Abstract A novel design of the dielectric barrier discharge (DBD) actuator/sensor is proposed for mapping the location of icing on a surface. The new design uses segmentation of the embedded electrode of the DBD actuator. Segmented DBD actuator/sensor devices were fabricated and experimentally tested in terms of mechanical, thermal and sensing abilities. The sensing capability of the new actuator was analyzed experimentally. Stationary and dynamic icing tests were conducted and the electrical characteristics of the DBD were measured. A parametric study on the effect of the electrode dimensions on the degree of sensitivity of the device was performed. Experimental results show that by using a segmented configuration it is possible to sense the onset of ice formation and also to detect its location. Furthermore, it is possible to detect the initiation of the melting process and measure the time for the water/ice to be completely expelled from the surface. It is also shown that the segmented actuator has better deicing performance in comparison to the conventional actuators. It is also shown that the thermal and active flow control abilities are not compromised by the segmented configuration and thus this device may perform deicing, ice formation and location detection and active flow control.

The Ice Test in Myasthenia Gravis: Who Should Do it, When, and Why?

During the past 50 years, I have diagnosed and managed hundreds of patients with myasthenia gravis (MG) and large numbers with ptosis due to other

Experimental Investigation on Uniaxial Unconfined Compressive Properties of Ice on Asphalt Pavement Surface

Mechanical deicing is a method to remove the ice on the pavement surface, and the ice strength directly affects the difficulty and effectiveness of the mechanical deicing. This paper aims to investigate the compression strength of ice to facilitate the deicing equipment to crush ice. In this paper, a large-scale freezing laboratory is employed to simulate low temperature environment, and the uniaxial unconfined compressive tests of artificial fresh-water ice under different temperature conditions are carried out through the uniaxial loading system. The compressive strength and modulus of ice are obtained when the substrate is asphalt pavement. The test result shows that the ice compressive strength and modulus respectively distribute from 0.36 MPa to 3.67 MPa and 11.7 MPa to 359.1 MPa when ice temperature varies from -0.7℃ to -7.5℃. The relations between ice temperature and compressive strength are approximately in linear manner, while the relation of compressive modulus and ice temperature shows good power function and exponential relationships respectively when ice temperature ranges from -8℃ to -5℃ and from -5℃ to 0℃. Furthermore, the failure mechanism of ice under relatively lower temperature is due to the development of cut-through cracks inside the ice. The failure mode divides into shear failure and ductile failure and the failure ice is mainly composed of large ice strips and bulks. For the ice with relatively higher temperature especially the ice close to melting point temperature, the ice failure mode is compressive and ductile, and the failure ice is mainly composed of granular ice crystals.

THE COURSE'S "THE TESTING OF INTERNAL COMBUSTION ENGINES" TEACHING METHODOLOGY DEVELOPMENT IN DOMECTIC EDUCATIONAL INSTITUTIONS - FRAGMENTS OF HISTORY

Considered are the main milestones of history of the course "The testing of ICE " teaching in the universities from the inception of this course to the present days. It is shown that the specialists who took a training course in this academic discipline and gave it priority in their work got a particular importance at engine manufacturing enterprises, since they began to play the role of experts in assessing the progressiveness of a particular solutions while developing new and improving old designs of domestic internal combustion engines. The information on the main textbooks and teaching aids on this subject is provided. The painful issue of the initial basing of the taught material on the backlog of foreign sources of training is touched on, which after 100 years continues to dampen the scientific and pedagogical staff of the Kharkov school of engine building that already has rich own experience in all types of ICE testing. The analysis of the reasons for the drop in students' interest in self-study of modern educational literature on the ICE testing is carried out. It is noted that in the current situation in Ukraine and in the world, the revival of this interest will depend first of all on the ability to properly manage the vast experience gained in organizing and conducting engine tests at the Kharkiv Engine Design Bureau and the Head Specialized Engine Design Bureau, and create a new format of the local electronic tutorials not in the form of a copy of a regular printed publication, but in the form of a whole software training complex with specific presentation materials, photos and video examples in each topic.

Characteristics of icing without icicle on insulators under natural conditions

Icing on insulators seriously threatens the safe and stable operation of transmission lines. Most of the existing research has focused on the flashover characteristics of ice-covered insulators, lacking attention to the icing process on insulators. In order to reveal the mechanism of insulator icing, and lay the foundation for further establishment of insulator ice flashover model, this paper studies the characteristics of insulator icing without icicle. The characteristics of icing processes including the collision and freezing of water droplets, the generation and flowing of water film are analysed. On this basis, a three-dimensional numerical calculation model of insulator icing without icicle is established by using boundary element method, and the expressions of the local icing weight and thickness on the insulator surface are derived through the droplet local collision efficiency and freezing efficiency. Moreover, the time-varying characteristics of icing parameters are simulated. And the related icing tests are conducted on two kinds of insulators with different structures at Xuefeng Mountain. The results show that the distribution of collided water droplets and water film on the insulator surface will change with the increasing ice weight. Under natural conditions, compared with the aerodynamic insulator LDQ-100, the insulator LXY-120 with a smaller skirt diameter and a larger inclination angle can have a faster icing rate. However, at the insulator edge, the insulator LDQ-100 with a thinner shed has a greater icing rate of thickness. Compared with the test results, the simulation error of the model in this paper is within 15%.

Influence of electric field on the ice‐coating process of insulators with a different dielectric surface

Studying the influence of electric field on the icing process of insulators with various dielectric surfaces is of great importance to the design of external insulation. This study established a finite element model to simulate the distribution of electric field around various insulator strings. Energised and non-energised icing tests were conducted to obtain the influence rules of electric field on the insulator icing process. The results of water droplets freeze experiment provided microscopic explanation of icing tests. Research results indicate that electric field and surface dielectrics have influence on the appearance, density and mass of ice on insulators. In microcosmic view, water droplets on super-hydrophobic surface correspond to longer freezing time and smaller average diameters, which leads to the better anti-icing character of super-hydrophobic insulator. Different types of ice branches appear in the water droplets freezing process on various dielectric surfaces. Owing to the polarisation effect, electric field can inhibit the formation and growth of ice branch, which contributes to different anti-icing characters of various dielectric surfaces in electric field. The effect of dielectric surface on insulator icing process mainly act at the initial period, surface coatings of insulators are not suggested to be applied in heavily icing area.